I have freinds running 9 second all steel Darts with willwoods and heavier cars as daily drivers without issue's.
Rick has been know to make mistakes and more likey has taken that info about the brakes directly from ethier or both MP and/or Willwood themselfs. No disrespect to the man intended.
The brakes were NOT design to be on the street as everyday brakes and did not get a D.O.T. approval or one was not applied for. Willwood also set a weight/track limit on there useage.